1. Technical Field
The invention relates to an arrangement for fastening a press jacket to an end of a press roll, whereby an edge of the press jacket is bent over the edge of the press roll end, onto its end surface, and the jacket is pressed by means of separate fastening segments against the surface of the roll end, and whereby openings are formed in the press jacket for fastening bolts of the fastening segments, to allow the fastening bolts to extend through the openings to the press roll end, and holes are formed at the edge of the press jacket for the jacket to be tightened in its place before the fastening segments are tightened into place.
2. Description of the Related Art
Press rolls are used, to some extent, in a press section of a paper machine. A flexible press jacket is fastened to the ends of the roll, the jacket rotating with the ends to provide a press nip or a zone against a counter roll. Within a press roll jacket of this type there is also a body going through the roll, the body being either stationary or a body part rotating with the roll. This kind of a solution is disclosed for instance in Finnish Patent 85 167.
A problem in prior art solutions is that the press jacket needs to be symmetrically and co-axially fastened to the roll ends in order to obtain a well-functioning roll structure. However, when a press jacket made of a relatively hard material, such as polyurethane or the like, is used, it is difficult to fasten the jacket because urethane is a fairly stiff material and does not bend easily. It is therefore difficult to have the press jacket centered and to form a sealed structure when a structure is to be obtained in which the press jacket and the ends are arranged to form together a sealed structure which would not, for instance, allow the lubricant inside the press jacket, between the jacket and the roll body, to be pressed out.
The solution disclosed in Finnish Patent 85 167 comprises evenly spaced pin-shaped projections or bolts arranged at a given radius on the outer end surface at the roll end and dozens of tongues formed at the edge of the press jacket, with groove-shaped openings, into which the projections fit, between the tongues. In the solution concerned, said dozens of tongues are used to tighten the press jacket edge so that the projections press against the groove bases between the tongues, thus centering the press jacket in relation to the roll end. A sealed structure with respect to the roll end is, in turn, obtained by means of segments fastened to the roll end, the segments pressing the press jacket edge bent towards the roll axle against the roll end.
A problem in the solution in question is that, in practice, the dozens of fastening tongues are difficult to fasten and handle when the press jacket edge is being fastened and, should the tongues be fastened in an incorrect order, the jacket becomes unsymmetrically and unevenly fastened. It is also difficult and time-consuming to draw a jacket edge comprising dozens of tongues in its place over the roll body and the roll ends, especially when the ends are crossed.
An object of the present invention is to provide an arrangement for fastening the jacket to the press roll end in such a way that the above mentioned problems are avoided and a simpler and easier handling of the press jacket is provided. The arrangement of the invention is characterized in that thinnings are formed at regular intervals at the edge of the press jacket, said intervals being such that the fastening bolts of the fastening segments are always positioned at one of the thinnings; that the holes at the edge of the press jacket are formed between said thinnings in unthinned edge portions of the press jacket, aligned substantially at the same position in the axial direction of the press jacket; that, when the press jacket is mounted onto the press roll end, the jacket edge is fastened to the press roll end by means of said holes, at predetermined intervals on the circumference around the roll axle, by using fastening members going through said holes; and that said openings formed for the fastening bolts are holes formed at respective thinnings, the width of the holes in the axial direction of the press jacket being such that, when the press jacket is mounted in its place, the fastening bolts do not touch the hole edges in the radial direction of the roll end.
An essential idea in the invention is that in the edge zone of the press jacket end are formed fastening holes at regular intervals, the holes allowing the jacket edge to be centrally fastened in a simple manner for instance to pins fixed to the roll end portion beyond the fastening segments. Another essential idea in the invention is that the press jacket edge is thinned between the fastening holes so that when the press jacket is tightened by means of the fastening segments against the roll end, the material in the thinned portion can press into the space provided by the thinning in such a way that folds, or the like, thicker than the original thickness of the jacket are not formed at the fastening segments. Unexpectedly, it was observed that the use of both separate guiding pins or bolts and fastening holes at the ends of the tongues causes mounting problems, which can be avoided by using only fastening holes at the edges, the holes being engaged with correctly positioned fastening pins. It was also unexpectedly observed that it is not necessary to form separate tongues by cutting. Instead, it is sufficient that the press jacket is thinned at the fastening segments, so they do not cause folded portions thicker than the press jacket, whereby a sealed, easily mountable whole can be obtained. Consequently, it is also possible to provide wider holes for the fastening bolts, so the press jacket does not rest against the bolts and the jacket sets more naturally and freely into a correct position.
An advantage of the invention is that when the edge of the press jacket is formed in a manner according to the invention, problems caused by the handling of separate tongues are avoided. Further, the edge of the press jacket can be, when necessary, cut at some points of the thinnings to form a few broader tongues that have, however, said thinned portion between the fastening holes. A further advantage of the invention is that separate grooves and projections adjusted to the grooves are not needed for the centering of the press jacket, because the holes formed at the edge of the jacket and the fastening pins at the roll end allow the jacket to be centered with a sufficient accuracy, without additional measures being needed.